Ultra-wideband signal amplifier

ABSTRACT

Amplifier for an ultra-wideband (UWB) signal receiver having a signal input ( 15 ) for receiving an ultra-wideband signal which is sent by a transmitter ( 1 ) and which is transmitted in a sequence of transmission channels (K.sub.i) (which each have a particular frequency bandwidth) which has been agreed between the transmitter ( 1 ) and the receiver ( 4 ); a transistor ( 18 ) whose control connection is connected to the signal input ( 15 ); a resonant circuit ( 26, 30, 31 ) which is connected to the transistor ( 18 ) and whose resonant frequency can be set for the purpose of selecting the transmission channel (K.sub.i) in line with the agreed sequence of transmission channels; and having a signal output ( 29 ) for outputting the amplified ultra-wideband signal, the signal output being tapped off between the transistor ( 18 ) and the resonant circuit.

FIELD

The invention relates to an amplifier for an ultra-wideband (UWB) signalamplifier.

BACKGROUND

UWB (Ultra Wide Band) technology is capable of transmitting data at ahigh data transmission rate within a limited range.

The channel capacity is dependent on the available channel bandwidth. Inline with Shannon's equation, the channel capacity is calculated as:C=BWLOG 2(1+SNR) where C is the channel capacity in bits per second, BWis the available channel bandwidth in Hz, and SNR is the signal-to-noiseratio.

Ultra-wideband (UWB) technology provides a very high level of frequencybandwidth. First-generation UWB systems provide a frequency bandwidth ofbetween 3.1 and 5 GHz, and UWB systems from subsequent generationsprovide a frequency bandwidth of between 3.1 and 10.6 or between 3.1 and8 GHz. The high level of available channel bandwidth means that thetransmission capacity is very high. The low signal transmission powersmeans that the range of UWB transmitters is relatively short and is nomore than 10 meters.

FIG. 1 shows a UWB arrangement based on the prior art. A transmitteruses a transmission antenna to send a UWB signal to a reception antennaon a receiver. The UWB receiver contains a bandpass filter BPF whichallows signals to pass in the admissible spectrum of the UWB system, forexample in a frequency range between 3.1 and 10.6 GHz. The UWB receivedsignal is then amplified by a wideband amplifier with little noiseoutput. The wideband LNA (Low Noise Amplifier) has its output connectedto the signal processing circuit in the receiver.

FIG. 2 shows a wideband LNA based on the prior art, as is described inR. Gilmore and L. Besser “Practical RF Circuit Design for modernWireless Systems”, volume II Active Circuits and Systems ISBN1-58053-522-4. The wideband signal amplifier for amplifying the UWBreceived signal based on the prior art is designed such that itamplifies the entire UWB signal spectrum in a frequency range between3.1 and 10.6 GHz, for example. The very high frequency range which needsto be amplified uniformly by the wideband amplifier means that thecircuit complexity for such a wideband LNA based on the prior art isvery high. In addition, the wideband LNA based on the prior art has thedrawback that it has a very high power consumption.

In the case of ultra-wideband systems based on the prior art, there aretwo fundamentally different embodiments. In DSS (Direct Spread Spectrum)UWB systems, the entire wideband frequency spectrum is used fortransmitting the UWB signal. In a multiband UWB system, the widebandfrequency spectrum, which ranges from 3.1 to 10.6 GHz, for example, isdivided into frequency bands which have a minimum bandwidth of 500 MHz.In the case of this multiband UWB, the transmitter transmits the UWBtransmission signal in different frequency bands or channels in linewith a prescribed frequency hopping scheme, which is also known to theassociated receiver. If the entire UWB frequency band, which ranges from3.1 to 10.6 GHz, is divided into 15 frequency bands, for example, i.e.15 different transmission channels, the transmitter hops to and frobetween the various channels K.sub.i during transmission in line with aprescribed signal hopping scheme. By way of example, the transmitterhops to the channel K.sub.2, then to channel K.sub.3, then to channelK.sub.7 and finally back to channel K.sub.2. The channel hopping schemein question is then K.sub.2, K.sub.3, K.sub.7.

In this case, the transmission channel hopping scheme may comprise allor just some of the possible transmission channels.

To date, multiband UWB receivers based on the prior art have also usedwideband signal amplifiers which have the aforementioned drawbacks, suchas high circuit complexity and high power consumption.

It is therefore the object of the present invention to provide a signalamplifier for a UWB receiver which is simple to implement in terms ofcircuitry and has a low power consumption.

The invention achieves this object by means of an amplifier having thefeatures cited in patent claim 1.

The invention provides an amplifier for an ultra-wideband (UWB) signalreceiver having a signal input for receiving an ultra-wideband signalwhich is sent by a transmitter and which is transmitted in a sequence oftransmission channels (which each have a particular frequency bandwidth)which has been agreed between the transmitter and the receiver, atransistor whose control connection is connected to the signal input, aresonant circuit which is connected to the transistor and whose resonantfrequency can be set for the purpose of selecting the transmissionchannel in line with the agreed sequence of transmission channels, andhaving a signal output for outputting the amplified ultra-widebandsignal, the signal output being tapped off between the transistor andthe resonant circuit.

In one preferred embodiment of the inventive amplifier, the resonantcircuit has a coil and a plurality of capacitors which are connected inparallel.

In this case, each capacitor is preferably connected to a controllableswitch.

The switches are preferably switched on the basis of a control signalwhich is output by a control device.

In one preferred embodiment of the inventive amplifier, a cascode stageis provided between the transistor and the signal output.

In a first embodiment of the inventive amplifier, the transistors areMOS field-effect transistors.

In an alternative embodiment of the inventive amplifier, transistors arebipolar transistors.

In one preferred embodiment of the inventive amplifier, the frequencybandwidth of a transmission channel is approximately 500 MHz.

The transmission channel sequence is preferably agreed between thetransmitter and the receiver in an initialization mode.

In one preferred embodiment, a memory device is provided which is usedfor storing the agreed transmission channel sequence.

In one preferred embodiment, the receiver has a controller which appliessignal control words to an internal decoding circuit in the amplifier inline with the stored transmission channel sequence.

The decoding circuit preferably actuates the controllable switches tochange the resonant frequency of the resonant circuit.

In one preferred embodiment, a matching circuit for matching the inputimpedance of the amplifier to the impedance of a reception antenna onthe receiver is provided at the signal input of the amplifier.

In one preferred embodiment, the impedance matching is performed by thematching circuit on the basis of the channel control words which areapplied by the controller.

In one particularly preferred embodiment of the inventive amplifier, theamplifier is of fully differential design.

The text below describes preferred embodiments of the inventiveamplifier with reference to the appended figures in order to explainfeatures which are fundamental to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the figures:

FIG. 1 shows a UWB circuit arrangement based on the prior art;

FIG. 2 shows a UWB wideband signal amplifier based on the prior art;

FIG. 3 shows a UWB circuit arrangement based on the invention;

FIG. 4 shows a preferred embodiment of the inventive narrowband UWBsignal amplifier;

FIG. 5 shows a graph to explain the way in which the inventivenarrowband UWB signal amplifier works.

DETAILED DESCRIPTION

FIG. 3 shows a UWB circuit arrangement based on the invention. Atransmitter 1 uses a transmission antenna 2 to send a UWB signal to areception antenna 3 on a UWB receiver 4. The reception antenna 3 isconnected to a bandpass filter 6 in the receiver 4 via a line 5. Thebandpass filter 6 preferably filters all signals outside of the UWBfrequency range, which extends from 3.1 to 10.6 GHz, for example, inorder to suppress noise. The output of the bandpass filter 6 isconnected to the inventive UWB narrowband signal amplifier 8 via a line7. The amplifier 8 outputs the amplified signal via a line 9 to a signalprocessing circuit 10 within the receiver 4. The narrowband amplifier 8receives a control signal from an internal controller 12 in the receiver4 via control lines 11, the control signal being a channel word whichindicates that transmission channel in which the UWB signal is currentlybeing sent by the transmitter 1. The controller 12 is connected to anintegrated channel sequence memory 14 in the receiver 4 via lines 13.The channel sequence memory 14 stores the sequence of transmissionchannels which has been agreed between the transmitter 1 and thereceiver 4.

In an initialization phase or in an initialization mode, the transmitter1 and the receiver 4 agree a particular sequence of transmissionchannels. To this end, the UWB frequency band, which extends from 3.1 to10.6 GHz, for example, is divided into frequency bands having a width of500 MHz each, and is allocated to corresponding channels. In aninitialization mode, the transmitter 1 transmits the desired channelsequence in which it will send the UWB transmission signal to thereceiver 4 cyclically in future. An example of such a transmissionchannel sequence is K.sub.2, K.sub.1, K.sub.3, K.sub.7, K.sub.2

The channel sequence is agreed between the transmitter 1 and thereceiver 4. In a search mode, the receiver 4 checks all transmissionchannels until it has found a suitable transmitter 1. This can be donerelatively quickly in a UWB system when there are 15 data transmissionchannels, for example, which means that the power consumption isrelatively low in this search mode. When the receiver 4 has found theassociated transmitter 1 in the search mode, it receives from thetransmitter 1 the transmitted UWB signal, with the receiver 4 hopping toand fro between the various frequency bands in line with the agreedchannel sequence in order to operate in sync with the receiver 1. Tothis end, the inventive narrowband signal amplifier 8 receives a channelword KW indicating the respective present transmission channel from thecontroller 12 via the control lines 11.

FIG. 4 shows a preferred embodiment of the inventive narrowband signalamplifier 8.

In line with the preferred embodiment shown in FIG. 4, the signalamplifier 8 is of fully differential design. The signal amplifier 8 hasa signal input with two signal input connections 15-1, 15-2. The applieddifferential input signal, which is applied to the signal input 15 ofthe narrow band amplifier 8 by the bandpass filter 6 via the lines 7, issent to a matching circuit 16-1, 16-2 within the amplifier 8. Thematching circuit 16 matches the input impedance of the amplifier 8 tothe impedance of the reception antenna 3 on the receiver 4. Theimpedance matching takes place in frequency-dependent fashion and inline with the respective present transmission channel. To this end, theimpedance matching circuit 16 receives the channel word KW from thecontroller 12 via the control lines 11. In one preferred embodiment, thematching circuit 16-2 may have additional filters for noise-signalmatching. The matching circuit 16-1, 16-2 in the embodiment shown inFIG. 4 is connected to a gate connection of NMOS field-effecttransistors 18-1, 18-2 via lines 17-1, 17-2. The NMOS transistors 18-1,18-2 are connected to one another at a node 20 via lines 19-1, 19-2, thenode 20 being connected to a current source 21. The current source 21delivers a constant current which is offloaded to a negative supplyvoltage V.sub.ss.

The NMOS transistors 18-1, 18-2 are connected via lines 22-1, 22-2 toseries-connected NMOS transistors 23-1, 23-2 whose gate connectionsreceive a bias voltage V.sub.Bias via a line 24. The NMOS transistors23-1, 23-2 form a cascode stage 22 in the amplifier 8. The cascode stage23 is connected via lines 25-1, 25-2 to coils or inductors 26-1, 26-2which are supplied by a positive supply voltage VDD. At branching nodes27-1, 27-2, the output signal from the amplifier 8 is tapped off. Thebranching nodes 27-1, 27-2 are connected to the output signalconnections 29-1, 29-2 of the amplifier 8 via internal lines 28-1, 28-2.

The amplifier 8 also contains capacitors 30 a-1 . . . 30 a-n; 30 b-1 . .. 30 b-n which can be connected to branching nodes 32-1, 32-2 in theamplifier 8 by means of associated controllable switches 31. One side ofthe capacitors 30 has the negative supply voltage V.sub.SS applied toit. The controllable switches 31 are actuated by an internal switchactuation logic unit 34 via control lines 33-1, 33-1. The switchactuation logic unit 34 codes the channel word KW which is present onthe control line 11-3.

The UWB signal amplifier 8 of fully differential design which is shownin FIG. 4 has a first resonant circuit, which is formed by the coil 26-1and the capacitors 30 a, and a second resonant circuit, which is formedby the coil 26-2 and the capacitors 30 b. The two resonant circuits areof identical design. The resonant frequency of the two resonant circuitsis set on the basis of the applied channel word KW for the purpose ofselecting the transmission channel in line with the agreed sequence oftransmission channels K.sub.i.

FIG. 5 shows the ratio of the output power to the input power of theinventive narrowband UWB signal amplifier for various resonantfrequencies f.sub.c, with the resonant frequency of the resonantcircuits being shifted on the basis of the channel word KW. Thefrequency bandwidth of the resonant circuit is preferably the same asthe frequency bandwidth of a transmission channel, for example 500 MHz.The high transmission frequencies of the UWB systems mean that the coils26-1, 26-2 can be integrated in the form of spirally arranged conductortracks, for example.

The circuit complexity for the inventive UWB signal amplifier 8 shown inFIG. 4 is relatively low. The small number of required components meansthat also the power consumption of the inventive signal amplifier 8 islow.

The invention claimed is:
 1. An amplifier for an ultra-wideband signalreceiver having: a signal input for receiving an ultra-wideband signaltransmitted in a predetermined sequence of transmission channels; anamplifier element having an input connection coupled to the signalinput, and an output; a resonant circuit connected to the output of theamplifier element, the resonant circuit comprising at least oneinductance connected to an adjustable capacitance circuit, wherein theresonant circuit is configured to exhibit an adjustable resonantfrequency, the adjustable resonant frequency adjusted according to acontrol signal to select a channel from the predetermined sequence oftransmission channels; wherein the control signal is driven by dataassociated with the predetermined sequence of transmission channels;wherein the amplifier element is operable to amplify the ultra-widebandsignal provided at the signal input in a plurality of differingfrequency bands in an order dictated by the predetermined sequence oftransmission channels; and a signal output configured to provide theamplified ultra-wideband signal.
 2. The amplifier of claim 1, whereinthe amplifier element comprises a transistor.
 3. The amplifier of claim1, wherein the adjustable capacitance comprises: an adjustablecapacitance circuit having a plurality of capacitors connected tobranching nodes by associated controllable switches; and a switchactuation logic unit that controls the controllable switches accordingto the control signal.
 4. The amplifier of claim 3, wherein the controlsignal comprises a channel word.
 5. The amplifier of claim 1, furthercomprising a memory operably coupled to the amplifier, and configured tostore information relating to the predetermined sequence of transmissionchannels.
 6. The amplifier of claim 5, wherein a retrieval of theinformation stored in the memory dictates a content of the controlsignal.
 7. The amplifier according to claim 6, further comprising acontroller operably configured to adjust the adjustable resonantfrequency, wherein the controller is configured to retrieve theinformation stored in the memory and generate the control signal inresponse thereto.
 8. The amplifier according to claim 7, wherein: thecontroller is operably connected to provide a plurality of controlsignals to a switch actuation unit operably associated with the resonantcircuit, the control signals based on the transmission channel sequence;the resonant circuit includes a plurality of capacitors coupled inseries with corresponding switches; and the switch actuation unit isoperable to controllably actuate the switches in accordance with thecontrol signals.
 9. The amplifier according to claim 1, furthercomprising a cascade stage operably coupled between the amplifierelement and the signal output.
 10. The amplifier according to claim 1,wherein the amplifier element comprises a MOS field-effect transistor.11. The amplifier according to claim 1, wherein the amplifier elementcomprises a bipolar transistor.
 12. The amplifier according to claim 1,wherein the frequency bandwidth of a transmission channel is about 500MHz.
 13. The amplifier according to claim 1, further comprising amatching circuit coupled to the signal input, the matching circuitconfigured to match an input impedance of the amplifier to an impedanceof a reception antenna of the ultra-wideband receiver.
 14. The amplifieraccording to claim 13, wherein the matching circuit is operable toperform variable impedance matching as a function of the transmissionchannel sequence.
 15. An amplifier for an ultra-wideband signal receiverhaving: a differential signal input for receiving an ultra-widebandsignal transmitted in a predetermined sequence of transmission channels;a first amplification element having an input connection connected tothe differential signal input, and having a first output, and a secondamplification element having an input connection connected to thedifferential signal input, and having a second output; a first resonantcircuit connected to the first output of the first amplificationelement, the first resonant circuit having a first adjustable resonantfrequency, the first adjustable resonant frequency adjusted according tothe predetermined sequence of transmission channels; a second resonantcircuit connected to the second output of the second amplificationelement, the second resonant circuit having a second adjustable resonantfrequency, the second adjustable resonant frequency adjusted accordingto the predetermined sequence of transmission channels; and adifferential signal output coupled to the first and second outputs,respectively, and configured to provide the amplified ultra-widebandsignal, the differential signal output being tapped off at the firstoutput of the first amplification element, and at the second output ofthe second amplification element; wherein the amplifier is operable toamplify the ultra-wideband signal provided at the differential signalinput in a plurality of differing frequency bands in an order dictatedby the predetermined sequence of transmission channels.
 16. Theamplifier according to claim 15, further comprising a memory operablycoupled to the amplifier, and configured to store information relatingto the predetermined sequence of transmission channels.
 17. Theamplifier according to claim 15, wherein each of the first and secondresonant circuits comprises at least one inductive coil and anadjustable capacitance circuit.
 18. The amplifier according to claim 17,wherein each adjustable capacitance circuit includes a plurality ofcapacitors that are selectively connected in parallel.
 19. The amplifieraccording to claim 18, further comprising a first cascade stage operablycoupled between the first amplification element and the differentialsignal output, and a second cascade stage operably coupled between thesecond amplification element and the differential signal output.
 20. Theamplifier according to claim 15, wherein the first and secondamplification elements comprise first and second transistors,respectively.